drone

Concise Oxford English Dictionary © 2008 Oxford University Press:
drone/drəʊn/

▶verb make a continuous low humming sound.

■ speak tediously and at length: Jim droned on for an hour.

▶noun

• 1 a low continuous humming sound.

  ■ a pipe (especially in a set of bagpipes) or string used to sound a continuous note of low pitch.

• 2 a male bee which does no work in a colony but can fertilize a queen.

  ■ an idle person.

• 3 a remote-controlled pilotless aircraft.

– origin OE drān, drǣn ‘male bee’, from a W. Gmc verb meaning ‘resound, boom’.